diff --git a/api/src/com/cloud/agent/api/ClusterSyncAnswer.java b/api/src/com/cloud/agent/api/ClusterSyncAnswer.java
new file mode 100644
index 00000000000..858acb46439
--- /dev/null
+++ b/api/src/com/cloud/agent/api/ClusterSyncAnswer.java
@@ -0,0 +1,54 @@
+/*  Copyright (C) 2010 Cloud.com, Inc.  All rights reserved.
+ * 
+ * This software is licensed under the GNU General Public License v3 or later.
+ * 
+ * It is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or any later version.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ */
+
+package com.cloud.agent.api;
+
+import java.util.HashMap;
+
+import com.cloud.utils.Pair;
+import com.cloud.vm.VirtualMachine.State;
+
+public class ClusterSyncAnswer extends Answer {
+    long _clusterId;
+    HashMap<String, Pair<String, State>> _newStates;
+    int _type = -1; // 0 for full, 1 for delta
+    
+    public static final int FULL_SYNC=0;
+    public static final int DELTA_SYNC=1;
+    
+    public ClusterSyncAnswer() {
+    }
+    
+    public ClusterSyncAnswer(long clusterId, HashMap<String, Pair<String, State>> newStates, int type){
+        _clusterId = clusterId;
+        _newStates = newStates;
+        _type = type;
+        result = true;
+    }
+
+    public long getClusterId() {
+        return _clusterId;
+    }
+    
+    public HashMap<String, Pair<String, State>> getNewStates() {
+        return _newStates;
+    }   
+    
+    public boolean isFull(){
+        return _type==0;
+    }
+}
\ No newline at end of file
diff --git a/api/src/com/cloud/agent/api/ClusterSyncCommand.java b/api/src/com/cloud/agent/api/ClusterSyncCommand.java
new file mode 100644
index 00000000000..83b79cbbddb
--- /dev/null
+++ b/api/src/com/cloud/agent/api/ClusterSyncCommand.java
@@ -0,0 +1,65 @@
+/*  Copyright (C) 2010 Cloud.com, Inc.  All rights reserved.
+ * 
+ * This software is licensed under the GNU General Public License v3 or later.
+ * 
+ * It is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or any later version.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ */
+
+package com.cloud.agent.api;
+
+
+public class ClusterSyncCommand extends Command implements CronCommand {
+    int _interval;
+    int _skipSteps;  // skip this many steps for full sync
+    int _steps;
+
+    long _clusterId;
+    
+    public ClusterSyncCommand() {
+    }
+    
+    public ClusterSyncCommand(int interval, int skipSteps, long clusterId){
+        _interval = interval;
+        _skipSteps = skipSteps;
+        _clusterId = clusterId;
+        _steps=0;
+    }
+
+    @Override
+    public int getInterval() {
+        return _interval;
+    }
+    
+    public int getSkipSteps(){
+        return _skipSteps;
+    }
+    
+    public void incrStep(){
+        _steps++;
+        if (_steps>=_skipSteps)_steps=0;
+    }
+    
+    public boolean isRightStep(){
+        return (_steps==0);
+    }
+    
+    public long getClusterId() {
+        return _clusterId;
+    }
+
+    @Override
+    public boolean executeInSequence() {
+        return true;
+    }
+    
+}
\ No newline at end of file
diff --git a/core/src/com/cloud/hypervisor/xen/resource/XenServerPoolVms.java b/core/src/com/cloud/hypervisor/xen/resource/XenServerPoolVms.java
new file mode 100644
index 00000000000..2927a1388b3
--- /dev/null
+++ b/core/src/com/cloud/hypervisor/xen/resource/XenServerPoolVms.java
@@ -0,0 +1,85 @@
+package com.cloud.hypervisor.xen.resource;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.apache.log4j.Logger;
+
+import com.cloud.utils.Pair;
+import com.cloud.vm.VirtualMachine.State;
+
+ 
+public class XenServerPoolVms {
+    private static final Logger s_logger = Logger.getLogger(XenServerPoolVms.class);
+    HashMap<String/* clusterId */, HashMap<String/* vm name */, Pair<String/* host uuid */, State/* vm state */>>> _cluster_vms = 
+        new HashMap<String, HashMap<String, Pair<String, State>>>();
+
+    public HashMap<String, Pair<String, State>> getClusterVmState(String clusterId){
+        HashMap<String, Pair<String, State>> _vms= _cluster_vms.get(clusterId);
+        if (_vms==null) {
+            HashMap<String, Pair<String, State>> vmStates =  new HashMap<String, Pair<String, State>>();
+            _cluster_vms.put(clusterId, vmStates);
+            return vmStates;
+        }
+        else return _vms;
+    }
+    
+    public void clear(String clusterId){
+        HashMap<String, Pair<String, State>> _vms= getClusterVmState(clusterId);
+        synchronized (_vms) {
+            _vms.clear();
+        }
+    }
+    
+    public State getState(String clusterId, String name){
+        HashMap<String, Pair<String, State>> vms = getClusterVmState(clusterId);
+        Pair<String, State> pv = vms.get(name);
+        return pv.second();
+    }
+
+    public void put(String clusterId, String hostUuid, String name, State state){
+        HashMap<String, Pair<String, State>> vms= getClusterVmState(clusterId);
+        synchronized (vms) {
+            vms.put(name, new Pair<String, State>(hostUuid, state));
+        }
+    }
+    
+    public void remove(String clusterId, String hostUuid, String name){
+        HashMap<String, Pair<String, State>> vms= getClusterVmState(clusterId);
+        synchronized (vms) {
+            vms.remove(name);
+        }
+    }
+    
+    public void putAll(String clusterId, HashMap<String, Pair<String, State>> new_vms){
+        HashMap<String, Pair<String, State>> vms= getClusterVmState(clusterId);
+        synchronized (vms) {
+            vms.putAll(new_vms);
+        }
+    }
+    
+    public int size(String clusterId){
+        HashMap<String, Pair<String, State>> vms= getClusterVmState(clusterId);
+        return vms.size();
+    }
+  
+    
+    public static void main(String args[]){
+        XenServerPoolVms vms = new XenServerPoolVms();
+    }
+    
+    @Override
+    public String toString(){
+        StringBuilder sbuf = new StringBuilder("PoolVms=");
+        for (HashMap<String/* vm name */, Pair<String/* host uuid */, State/* vm state */>>  clusterVM: _cluster_vms.values()){
+            for (String vmname: clusterVM.keySet()){
+                sbuf.append(vmname).append("-").append(clusterVM.get(vmname).second()).append(",");
+            }
+        }
+        return sbuf.toString();
+    }
+    
+}
+